US4536855A - Impedance restoration for fast carry propagation - Google Patents

Impedance restoration for fast carry propagation Download PDF

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Publication number
US4536855A
US4536855A US06/452,596 US45259682A US4536855A US 4536855 A US4536855 A US 4536855A US 45259682 A US45259682 A US 45259682A US 4536855 A US4536855 A US 4536855A
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adder
carry
bit
accordance
arithmetic
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Expired - Fee Related
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US06/452,596
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English (en)
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Steven G. Morton
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ITT Inc
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International Telephone and Telegraph Corp
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Assigned to INTERNATIONAL TELEPHONE AND TELEGRAPH CORPORATION reassignment INTERNATIONAL TELEPHONE AND TELEGRAPH CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: MORTON, STEVEN G.
Priority to US06/452,596 priority Critical patent/US4536855A/en
Priority to NZ206166A priority patent/NZ206166A/en
Priority to AU21955/83A priority patent/AU2195583A/en
Priority to EP83112617A priority patent/EP0116710A3/fr
Priority to JP58239996A priority patent/JPS59121542A/ja
Priority to BE2/60303A priority patent/BE898544R/fr
Assigned to ITT CORPORATION reassignment ITT CORPORATION CHANGE OF NAME (SEE DOCUMENT FOR DETAILS). Assignors: INTERNATIONAL TELEPHONE AND TELEGRAPH CORPORATION
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F7/00—Methods or arrangements for processing data by operating upon the order or content of the data handled
    • G06F7/38—Methods or arrangements for performing computations using exclusively denominational number representation, e.g. using binary, ternary, decimal representation
    • G06F7/48—Methods or arrangements for performing computations using exclusively denominational number representation, e.g. using binary, ternary, decimal representation using non-contact-making devices, e.g. tube, solid state device; using unspecified devices
    • G06F7/50—Adding; Subtracting
    • G06F7/505—Adding; Subtracting in bit-parallel fashion, i.e. having a different digit-handling circuit for each denomination
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F7/00—Methods or arrangements for processing data by operating upon the order or content of the data handled
    • G06F7/38—Methods or arrangements for performing computations using exclusively denominational number representation, e.g. using binary, ternary, decimal representation
    • G06F7/48—Methods or arrangements for performing computations using exclusively denominational number representation, e.g. using binary, ternary, decimal representation using non-contact-making devices, e.g. tube, solid state device; using unspecified devices
    • G06F7/50—Adding; Subtracting
    • G06F7/501—Half or full adders, i.e. basic adder cells for one denomination
    • G06F7/503—Half or full adders, i.e. basic adder cells for one denomination using carry switching, i.e. the incoming carry being connected directly, or only via an inverter, to the carry output under control of a carry propagate signal
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2207/00—Indexing scheme relating to methods or arrangements for processing data by operating upon the order or content of the data handled
    • G06F2207/38—Indexing scheme relating to groups G06F7/38 - G06F7/575
    • G06F2207/3804—Details
    • G06F2207/386—Special constructional features
    • G06F2207/3868—Bypass control, i.e. possibility to transfer an operand unchanged to the output
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2207/00—Indexing scheme relating to methods or arrangements for processing data by operating upon the order or content of the data handled
    • G06F2207/38—Indexing scheme relating to groups G06F7/38 - G06F7/575
    • G06F2207/48—Indexing scheme relating to groups G06F7/48 - G06F7/575
    • G06F2207/4802—Special implementations
    • G06F2207/4804—Associative memory or processor

Definitions

  • the present invention relates generally to high speed digital logic circuitry in which digital signal propagation delay is greatly reduced.
  • the invention is applicable to any serial connection of digital logic circuits, such as carry circuits and to multiplexers in series.
  • the invention is particularly applicable to associative processors in which large numbers of carry circuits or multiplexers are connected in series.
  • Associative processors are processors which operate on many data objects simultaneously rather than sequentially as in a conventional processor.
  • Such an associative processor may be comprised of an array of single bit computers implemented in LSI.
  • Such cellular computers obey the same instruction simultaneously, each operating on its own data.
  • the cells in a row of the associative processor array can be dynamically (from one instruction to the next) configured into an arbitrary number of fields of arbitrary defined length (within the constraints of the width of the array). Each field can then operate independently as if it were a separate computer of the given word length, able to perform arithmetic and logical operation. These fields can all obey the same instruction simultaneously, or they may be selectively disabled under program control.
  • U.S. Pat. No. 3,728,532 Carry Skip-Ahead Network
  • Carry Skip-Ahead Network describes carry networks having a power-of-2 number of bits in which the number of connections between cells increases as the number of skipped bits increases, being four for a 4-bit block, thus increasing the cost of interconnection.
  • U.S. Pat. No. 3,925,651 Current Mode Arithmethic Logic Array shows a 4-bit arithmetic and logical unit built of current mode logic.
  • U.S. Pat. No. 4,229,803, I 2 L Full Adder and ALU shows an I 2 L arithmetic and logic unit.
  • the present invention describes an improved circuit for performing high speed arithmetic computations, and includes a mechanism for dynamically deleting faulty data bits in a configuration for minimizing propagation delay paths.
  • the invention is particularly applicable to an associative processor wherein the data word length and rate of flow of data may vary from one instruction to the next.
  • data propagation delay time is minimized as is the number of required circuit interconnections, thereby making the invention easily manufacturable on an LSI chip.
  • the advantages of the circuit design are multiplied in an associative processor, since such processors are highly reconfigurable and must be able to exclude unwanted bits from an arithmetic operation, to change data word sizes and to delete failed bits.
  • the present invention is advantageously implemented in arithmetic carry circuits and in cascaded multiplexer logic circuits, which may effectively be implemented in MOS (metal oxide semiconductor) integrated circuits, or in CMOS (complementary MOS) integrated circuits in which a plurality of stages of such circuits must be connected in series, i.e. eight, sixteen, thirty-two, etc., while still providing a rapid execution speed.
  • MOS metal oxide semiconductor
  • CMOS complementary MOS
  • FIG. 1A is a schematic of a known CMOS transmission gate.
  • FIG. 1B is a simplified representation of the schematic of FIG. 1A.
  • FIG. 1C is a schematic of a lumped circuit model of a known transmission gate.
  • FIG. 2 is a simplified schematic equivalent circuit of a known worst case transmission gate carry circuit.
  • FIG. 3A is a basic adder cell in accordance with the present invention.
  • FIG. 3B is a Carry Decision Logic Truth Table of the adder cell of FIG. 3A.
  • FIG. 4 is a multiple bit adder comprised of eight basic adder cells of the type illustrated by FIG. 3A.
  • FIG. 5 is a multiple bit adder with a bypassed bit in accordance with the present invention.
  • FIGS. 1A, 1B and 1C are illustrative of conventional circuit representations used in describing CMOS transmission gates.
  • FIG. 1A is a schematic of an explicit inverter wherein the transmission gate 10 is comprised of two series pass transistors 12 and 14, with transistor 12 being p-channel and transistor 14 being n-channel.
  • the control line 16 is high (logic 1), either one of transistors 12 and 14 may conduct, depending upon the states of the input signal on line 18 and the output signal line 20, and presenting a relatively low impendance path from input 18 to output line 20.
  • the CMOS transmission gate is considered active (ON).
  • FIG. 1A illustrates a lumped circuit model of a CMOS transmission gate.
  • the capacitances Co an CI are approximately equal to 0.5 picofarad (pF) and the resistance R is approximately equal to 1000 ohms.
  • FIG. 2 a simplified equivalent circuit for a worst case CMOS transmission gate carry circuit is illustrated by a plurality of lumped circuit models in series, of the type shown by FIG. 1C.
  • Such a series of transmission gates typically occurs in a long carry propagate chain.
  • the capacitance C between each of nodes 1 through 8 to ground is equal to C I +C o .
  • the resistive impedance R to charge C at node 1 is equal to R+S, where S is the source impedance.
  • the resistive impedance to charge C at Node 4 is 4R+S, and so on for each node.
  • each transmission gate would be replaced by a buffer circuit, such as 114 in FIG. 3A.
  • a buffer circuit such as 114 in FIG. 3A.
  • Such a buffer when active would present an impedance of approximately 1000 ohms to either ground or VCC, and the output would be the same state as the input.
  • the propagation delay through a buffer is substantially longer than the propagation delay through an isolated transmission gate.
  • Optimum performance can be derived through a combination of transmission gates and buffers.
  • a sum circuit 102 may be of conventional design, wherein the sum is true when one and only one of the three inputs A, B and Carry In is true, or when all three of the inputs are true.
  • the carry circuit 104 uniquely provides a choice on lines 106 and 108 of carry propagation.
  • Carry In data from line 110 may flow through either CMOS transmission gate pass transistors 112 or through buffer 114 depending upon the value of configuration dependent information IRM on line 116, and fault location information on line 118.
  • Impedance Restoration Mask is symbolized by IRM and fault location information is denoted by Bypass.
  • An Impedance Restoration Mask may be defined as a bit pattern that selects where buffers are to be used rather than transmission gates in order to minimize worst case propagation delays.
  • Carry decision logic circuit 130 is a logic circuit which implements the carry decision logic truth table of FIG. 3B. Thus, depending upon the logic state of inputs A and B, Carry One (CO), Carry Propagate (CP) and Carry Zero (CZ) have the logic states shown in FIG. 3B.
  • Carry Propagate is AND'ed with IRM and Not Bypass (complement of Bypass) at AND gate 132. Not Bypass and Carry One are NAND'ed at NAND gate 134. Not IRM and Carry Propagate are AND'ed at AND gate 136. The output of AND gate 136 is OR'ed with Bypass on line 118 at OR gate 138. Not Bypass and Carry Zero are AND'ed at AND gate 140.
  • MOS transmission gate 120 is either an open circuit or is coupled to voltage Vcc, which is 5v or 10v dc preferably.
  • Buffer 114 either connects Carry In from line 110 to Carry Out on line 124 or is an open circuit.
  • CMOS transmission gate 112 connects Carry In from line 110 to Carry Out on line 124 or is an open circuit.
  • MOS transmission gate 122 is connected either to supply ground or is an open circuit.
  • the multiple bit adder is configured of a plurality of basic adder cells, each of which is of the type described with reference to FIGS. 3A and 3B.
  • Adder cells 202, 204, 206, 210 and 214 each may therefore activate a transmission gate from the cell Carry In to Carry Out, gates 222, 224, 226, 228, 230 and 232 respectively, each being of the type described with reference to gate 112 of FIG. 3A.
  • Adder cells 208 and 216 each may activate a buffer from the cell Carry In to Carry Out, buffers 234 and 236 respectively, each being of the type described with reference to buffer 114 of FIG. 3A.
  • the A and B logical inputs for worst case propagation delay to cells 202 through 216, shown as Ao and Bo for cell 202 through A 7 and B 7 for cell 216, are shown in Table 1.
  • the table also shows IRM O through IRM 7 , which minimizes this delay, and Bypass 0 through Bypass 7 , which select all cells to participate in the addition.
  • the propagation delay from Carry In on input 218 to Carry Out at output 220 is about three nanoseconds (3 nS) for the first transmission gate 222, 4 nS for the second gate 224, 5 nS for the third gate 226, plus 10 nS per buffer, for a total propagation delay of two times 22 nS, or 44 nS, compared to eight times 10 nS or 80 nS, if all buffers were to be used.
  • the sums ⁇ 0 through ⁇ 7 are typically coupled to the input of a memory whose outputs are the source of inputs A 0 through A 7 and B 0 through B 7 . The sum may thus be used in subsequent calculations.
  • the Carry Out is typically coupled to the input of the next section of the adder for an adder that has more than eight bits, or to a flip flop for storage for use in subsequent calculations.
  • IRM 0 through IRM 7 are typically obtained from a register that is loaded by the system controller when word sizes are changed.
  • Bypass 0 through Bypass 7 are typically obtained from a register that is loaded by the system controller when defects are detected or when bits are otherwise to be excluded from an operation.
  • the circuit performance for all transmission gates of adder 200 yields a very slow rise and fall time signal and has a resulting propagation delay time for 8-bits comparable to a circuit having all buffers instead of transmission gates.
  • FIG. 5 a block diagram of a multiple bit adder of the type which may advantageously be used in an associative processor is illustrated generally at 300.
  • Each of the basic adder cells 302, 304, 306, 308, 310, 312, 314 and 316 is of the type described with reference to FIG. 3A. It is desired that one of the center bits not participate in the addition process, but that the remaining bits be added.
  • the non-participating bit is called the "bypassed bit", and by way of example, will occur in adder 308.
  • the bypassed bit is omitted from the addition either because it or that bit of the adder is faulty or because inputs A 7-0 and B 7-0 have a peculiar bit in the middle of them that is not to be added. Such a peculiar bit might for example be a status bit in a telemetry application.
  • FIG. 3 illustrates how the Bypass signal is coupled to the basic adder.
  • the Bypass signal may come from a register that is external to the adder.
  • the Impedance Restoration Mask (IRM) may come from an external register.
  • the transmission gate 112 of FIG. 3A is turned ON and all other elements 120, 114 and 122 of the basic adder of FIG. 3A are turned OFF whenever the Bypass signal is true (logic 1).
  • the basic adder cells 302, 304, 306, 308, 312 and 314 may actuate transmission gates 318, 320, 322, 324, 326 and 328 respectively.
  • Adder cells 310 and 316 may activate buffers 330 and 332 respectively.
  • the Bypass bit to a cell is false, the choice of whether a cell may activate a buffer or a transmission gate is determined by IRM 7-0 .
  • a transmission gate is turned ON when the Bypass signal is true (logic 1). While the enabling of a transmission gate is usually preferable to the buffer because the transmission gate is faster than the buffer, it is noted that the buffer could be enabled rather than the transmission gate if so desired.
  • FIG. 5 is illustrative of an Impedance Restoration Mask (IRM) that enables buffer 330 in the bit following the bypassed bit. If the bit (denoted by X) were not bypassed, the buffer or transmission gate in adder 308 would have otherwise been enabled. This bypassing of a faulty bit functions to minimize the number of adder bits in a series, thereby maintaining a high speed of data propagation.
  • IRM Impedance Restoration Mask
  • a and B logical inputs to adder cells 302 through 316 shown as Ao and Bo for cell 302 through A 7 and B 7 for cell 316 are shown in Table II, as are IRM 0 through IRM 7 and Bypass 0 through Bypass 7 .
  • the sums ⁇ 0 through ⁇ 6 , and ⁇ x are coupled to the input of a memory whose outputs are A 0 through A 7 and B 0 through B 7 .
  • the sum ⁇ 0-6 may thus be used in subsequent calculations.
  • the sum ⁇ x from adder 308 may also be discarded.
  • the CARRY IN on line 334 is derived from the Carry Out of a previous stage, or may be connected to a variety of sources such a logic 0 for "add A to B with no carry in", or a Carry flip-flop for "add A to B with carry flipflop".
  • the CARRY OUT on line 336 is coupled to the input of the next section of the adder for an adder with more than eight bits, or to a flip-flop for storage for use in subsequent calculations.
  • IRM 0 through IRM 7 and Bypass 0 through Bypass 7 are derived from registers that are loaded by the system controller when word sizes are changed, defects are detected, or bits are otherwise excluded from an operation.
  • the technique of the present invention is applicable to other logic circuits than adders, and is generally applicable to any functional logic unit having an input, an operation performed, and an output which is passed on to the next stage.
  • a series connection of exclusive OR gates may have a bit left out of an operation. A bit is left out by setting the Bypass signal true (logic 1) to the particular functional logical unit implementing the exclusive OR function.
  • a set of values for the Impedance Restoration Mask is chosen to minimize the worst case signal propagation time. The choice depends upon the LSI circuit fabrication technique, interface considerations between cells, and upon the data word size. It is assumed in the example of FIG. 4 that only every fourth buffer may need to be activated, leaving the three intervening transmission gates potentially active.
  • the value of the Impedance Restoration Mask may be loaded into a register which sends the information to the adder at run time, or may be hardwired at the time of manufacture, depending upon the reconfigurability of the circuit. Arbitrarily long adder chains can be fabricated, and the propagation delay time resulting from the optimum usage of buffers is only a small fraction of the time required fo an all-buffer or all-transmission gate implementation.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Pure & Applied Mathematics (AREA)
  • Mathematical Analysis (AREA)
  • Computational Mathematics (AREA)
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US06/452,596 1982-12-23 1982-12-23 Impedance restoration for fast carry propagation Expired - Fee Related US4536855A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
US06/452,596 US4536855A (en) 1982-12-23 1982-12-23 Impedance restoration for fast carry propagation
NZ206166A NZ206166A (en) 1982-12-23 1983-11-04 Arithmetic adder:carry signal of selectable propagation delay
AU21955/83A AU2195583A (en) 1982-12-23 1983-12-05 Arithmetic adder circuit
EP83112617A EP0116710A3 (fr) 1982-12-23 1983-12-15 Restauration d'impédance pour la propagation rapide du report
JP58239996A JPS59121542A (ja) 1982-12-23 1983-12-21 加算器
BE2/60303A BE898544R (fr) 1982-12-23 1983-12-23 Calculateur associatif permettant une multiplication rapide.

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US06/452,596 US4536855A (en) 1982-12-23 1982-12-23 Impedance restoration for fast carry propagation

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US (1) US4536855A (fr)
EP (1) EP0116710A3 (fr)
JP (1) JPS59121542A (fr)
AU (1) AU2195583A (fr)
BE (1) BE898544R (fr)
NZ (1) NZ206166A (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4707800A (en) * 1985-03-04 1987-11-17 Raytheon Company Adder/substractor for variable length numbers
US4739503A (en) * 1986-04-21 1988-04-19 Rca Corporation Carry/borrow propagate adder/subtractor
US4860242A (en) * 1983-12-24 1989-08-22 Kabushiki Kaisha Toshiba Precharge-type carry chained adder circuit
US5040139A (en) * 1990-04-16 1991-08-13 Tran Dzung J Transmission gate multiplexer (TGM) logic circuits and multiplier architectures
US5065353A (en) * 1989-03-31 1991-11-12 Hitachi, Ltd. Adder control method and adder control circuit
US5162666A (en) * 1991-03-15 1992-11-10 Tran Dzung J Transmission gate series multiplexer
US5200907A (en) * 1990-04-16 1993-04-06 Tran Dzung J Transmission gate logic design method
US20100042903A1 (en) * 2008-08-15 2010-02-18 Lsi Corporation Reconfigurable adder

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61240330A (ja) * 1985-04-18 1986-10-25 Toshiba Corp 加算回路
RU2006143864A (ru) 2006-12-12 2008-06-20 Закрытое акционерное общество "Научно-исследовательский институт Аджиномото-Генетика" (ЗАО АГРИ) (RU) СПОСОБ ПОЛУЧЕНИЯ L-АМИНОКИСЛОТ С ИСПОЛЬЗОВАНИЕМ БАКТЕРИИ СЕМЕЙСТВА ENTEROBACTERIACEAE, В КОТОРОЙ ОСЛАБЛЕНА ЭКСПРЕССИЯ ГЕНОВ cynT, cynS, cynX, ИЛИ cynR, ИЛИ ИХ КОМБИНАЦИИ

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3654394A (en) * 1969-07-08 1972-04-04 Gordon Eng Co Field effect transistor switch, particularly for multiplexing
US3728532A (en) * 1972-01-21 1973-04-17 Rca Corp Carry skip-ahead network
US3766371A (en) * 1970-07-31 1973-10-16 Tokyo Shibaura Electric Co Binary full adder-subtractors
US3925651A (en) * 1975-03-26 1975-12-09 Honeywell Inf Systems Current mode arithmetic logic array
US4052604A (en) * 1976-01-19 1977-10-04 Hewlett-Packard Company Binary adder
US4229803A (en) * 1978-06-02 1980-10-21 Texas Instruments Incorporated I2 L Full adder and ALU
US4357675A (en) * 1980-08-04 1982-11-02 Bell Telephone Laboratories, Incorporated Ripple-carry generating circuit with carry regeneration
US4504749A (en) * 1981-07-20 1985-03-12 Takeda Riken Co., Ltd. Delay pulse generating circuit

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3654394A (en) * 1969-07-08 1972-04-04 Gordon Eng Co Field effect transistor switch, particularly for multiplexing
US3766371A (en) * 1970-07-31 1973-10-16 Tokyo Shibaura Electric Co Binary full adder-subtractors
US3728532A (en) * 1972-01-21 1973-04-17 Rca Corp Carry skip-ahead network
US3925651A (en) * 1975-03-26 1975-12-09 Honeywell Inf Systems Current mode arithmetic logic array
US4052604A (en) * 1976-01-19 1977-10-04 Hewlett-Packard Company Binary adder
US4229803A (en) * 1978-06-02 1980-10-21 Texas Instruments Incorporated I2 L Full adder and ALU
US4357675A (en) * 1980-08-04 1982-11-02 Bell Telephone Laboratories, Incorporated Ripple-carry generating circuit with carry regeneration
US4504749A (en) * 1981-07-20 1985-03-12 Takeda Riken Co., Ltd. Delay pulse generating circuit

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4860242A (en) * 1983-12-24 1989-08-22 Kabushiki Kaisha Toshiba Precharge-type carry chained adder circuit
US4707800A (en) * 1985-03-04 1987-11-17 Raytheon Company Adder/substractor for variable length numbers
US4739503A (en) * 1986-04-21 1988-04-19 Rca Corporation Carry/borrow propagate adder/subtractor
US5065353A (en) * 1989-03-31 1991-11-12 Hitachi, Ltd. Adder control method and adder control circuit
US5040139A (en) * 1990-04-16 1991-08-13 Tran Dzung J Transmission gate multiplexer (TGM) logic circuits and multiplier architectures
US5200907A (en) * 1990-04-16 1993-04-06 Tran Dzung J Transmission gate logic design method
US5162666A (en) * 1991-03-15 1992-11-10 Tran Dzung J Transmission gate series multiplexer
US20100042903A1 (en) * 2008-08-15 2010-02-18 Lsi Corporation Reconfigurable adder
US8407567B2 (en) * 2008-08-15 2013-03-26 Lsi Corporation Reconfigurable adder

Also Published As

Publication number Publication date
EP0116710A3 (fr) 1986-11-20
BE898544R (fr) 1984-04-25
EP0116710A2 (fr) 1984-08-29
JPS59121542A (ja) 1984-07-13
NZ206166A (en) 1986-12-05
AU2195583A (en) 1984-06-28
JPH0337211B2 (fr) 1991-06-04

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